Various types of polyethylenes are known in the art and each type has various applications. For example, low density polyethylene is generally prepared at high pressure using free radical initiators (known in the industry as “LDPE”). LDPE is also known as “branched” or “heterogeneously branched” polyethylene because of the relatively large number of branches extending from the polymer backbone. Polyethylene in the same density range, i.e., 0.916 to 0.950 g/cm3, which is linear and does not contain long chain branching is known as “linear low density polyethylene” (“LLDPE”) and may be produced, for example in a gas phase process, with conventional Ziegler-Natta catalysts or with metallocene compounds.
A large portion of global LDPE demand includes film, carrying bag, and sack applications. Some examples of these applications include agricultural, multi-layer, and shrink films, as well as reinforcements for levees. LDPE, which is soft, ductile, and flexible, is additionally utilized for strong, elastic goods, such as screw caps, lids, and coatings. Films made from LDPE, however, have limited impact resistance compared to the catalyst produced LLDPEs. Likewise, LLDPE's have a high impact resistance but are difficult to process. Blending these resins often creates a composition that is easier to process, but the desirable toughness of the LLDPE's is reduced. What would be desirable is to improve the processability of LLDPE-type resins while maintaining high tear and toughness in the films produced from such resins.
Thus, there is a need for new efficient and cost advantageous processes to produce polymers having a density from 0.900 to 0.950 g/cm3 that are strong but have improved processing. More specifically, there is a need for new and improved products produced from these branched polymers, in particular blown film.
Related references include U.S. Pat. No. 6,908,972, US 2013-0090433, US 2013-0085244, US 2013-0211009, US 2013-041119, WO 2012-133717, JP 2011225670A, JP2011089019A, JP2011137146, and Q. Yang et al. in 43 MACROMOLECULES 8836-8852 (2010).